1. Field of the Invention
The present invention relates to a gas composition detector, and more particularly to an oxygen concentration detector for detecting oxygen concentration in exhaust gas of a motor vehicle and a method for manufacturing the same. More specifically, the present invention intends to prevent tear-off of an electrode.
2. Description of the Prior Art
A prior art oxygen concentration detector includes an oxygen concentration detection element made of an oxygen ion conductive metal oxide, and conductive metal layers such as platinum (Pt) layers are formed as electrodes on the sides of the oxygen concentration detection element facing the gas to be examined and reference gas, respectively.
However, since the electrode facing the gas to be examined is exposed to the gas, it is torn off during the use over a long period where a flow rate or temperature of the gas to be examined such as exhaust gas of a motor vehicle changes materially, so that the detector can no longer operate. The causes of this problem lie in that the oxygen concentration detection element is made of a metal oxide while the electrodes coated thereon are made of a metal and they are incompatible with each other, and that the electrodes are merely deposited on the surfaces of the oxygen concentration detection element and hence the disposition strength is weak.